The 36-year-old, charismatic Mello ran on an anti-Trump message, and was initially hailed as a future template for Democratic candidates in 2018 and 2020. But he wound up calling a major divide among his supporters when it was revealed that he had sponsored a pro-life bill while serving in the Nebraska statehouse several years ago.

Sanders, along with other top supporters, initially defended Mello, saying the party should make room for pro-life Democrats. But, facing heavy blowback from abortion groups like Planned Parenthood, Democratic Party chairman Tom Perez officially announced that anyone who didn’t unequivocally support abortion was no longer welcome in the party.

Perez’s actions caused a major rift among Democrats, in the middle of what should have a winnable election—and likely contributed to Mello snatching defeat from the jaws of victory.

While Trump’s approval rating continues to hover below 50 percent, it’s clear that the Democrats will have to run on more than an anti-Trump message in 2018—and will have to mend their fractured ranks sooner rather than later.